1. Field of the Invention
This invention generally relates to a dampening disk assembly. More specifically, the present invention relates to a dampening disk assembly of a separated hub type.
2. Background Information
A clutch disk assembly or dampening disk assembly used for a clutch of a car has a clutch function of coupling and/or uncoupling a flywheel of the engine to the transmission shaft, and a dampening function of absorbing and dampening torsion vibrations transmitted from the flywheel. The clutch disk assembly basically includes a clutch disk, a pair of input plates, a hub and elastic portions. The pair of input plates are fixedly coupled to the clutch disk. The hub is disposed on the inner circumferential side of the input plate. The elastic portions elastically couple the hub and the input plates together for movement in a rotary direction. The elastic portions are disposed between the input plates and the hub, and are compressed in a rotary direction when the input plates rotate relatively against the hub. When the clutch disk is coupled with the flywheel, a torque is inputted to the input plates of the clutch disk assembly from the flywheel. The torque is transmitted to the hub via the elastic portions, and then is outputted to the shaft extending from the transmission. When a torque fluctuation is inputted to the clutch disk assembly from the engine, a relative rotation is caused between the pair of input plates and the hub, and the elastic portions are compressed repeatedly in a circular direction.
In addition, the clutch disk assembly typically includes a friction mechanism. The friction mechanism is disposed between the input plates and the hub, and generates a friction resistance when the input plates rotate relatively against the hub. The friction mechanism includes basically a plurality of washers and urging portions.
A clutch disk assembly of a separated hub type has a hub flange (separated flange), which is a flange of a conventional hub separated from a boss. In addition, in the clutch disk assembly of a separated hub type, the boss and the hub flange are coupled in a rotary direction by elastic portions with a low rigidity. The clutch disk assembly of this type allows a wider angular range of relative rotation between the input plates and the hub, and shows a two step rigidity (low rigidity and high rigidity).
The conventional clutch disk assembly of a separated hub type described above includes, for example, a small friction mechanism between a retaining plate (one of the pair of input plates) and the boss of the hub, and a large friction mechanism between the retaining plate and the hub flange. The large friction mechanism includes a first friction portion and a first urging portion. The first friction portion touches the hub flange, and is also connected with the retaining plate relatively non-rotatably and axially movably. The first urging portion is disposed between the first friction portion and the retaining plate, and urges the first friction portion toward the hub flange. The small friction mechanism includes a second friction portion and a second urging portion. The second friction portion touches the flange of the hub and is also connected with the retaining plate in a relatively unrotatable and axially movable manner. The second urging portion is disposed between the second friction portion and the retaining plate, and urges the second friction portion toward the flange side. Generally, the first friction portion is set to have a friction coefficient larger than that of the second friction portion. The first urging portion is set to have an urging force larger than that of the second urging portion. Consequently, the large friction mechanism generates a friction (high hysteresis torque) larger than that of the small friction mechanism.
When the hub flange rotates relatively against the hub within a first range of a torsion angle, the elastic portions with a low rigidity are compressed, and the second friction portion of the small friction mechanism slides against the flange of the hub, resulting in characteristics of low rigidity and low hysteresis torque. After the hub flange starts rotating together with the boss, a relative rotation occurs between the hub flange and the pair of input plates. Within the second range of torsional change, the elastic portions with a high rigidity are compressed between the hub flange and the pair of input plates, and the second friction portion of the large friction mechanism slides against the hub flange, resulting in a characteristic of a high rigidity and high hysteresis torque.
In the clutch disc assembly of a separated hub type mentioned above, both the first and second urging portions are supported by the retaining plate. In such an assembly, there is a danger that the retaining plate is deformed in an axial direction since urging force or resiliency of the first urging portion is large. That is, the axial position of the retaining plate tends to be shifted slightly due to the urging force of the first urging portion. If this happens, the angle of the second urging portion is also changed, and therefore its urging force may be altered. Therefore, hysteresis torque generated by the small friction mechanism cannot be stabilized.
In view of the above, there exists a need for a dampening disk assembly or a clutch disk assembly of a separated hub type, which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.